•Graphene oxide (FL-GOc) and reduced graphene oxide (FL-RGOc): XRD, TEM, XPS, REELS.•FL-GOc: stacking nanostructure—22×6nm (DxH), 0.9nm layers separation (XRD).•FL-RGOc: stacking nanostructure—8×1nm ...(DxH), 0.4nm layers separation (XRD).•Reduction: oxygen group degradation, decreasing distance between graphene layers.•Number of graphene layers in stacking nanostructure: 6–7 (FL-GOc), 2–3 (FL-RGOc).
The commercial and synthesised few-layer graphene oxide, prepared using oxidation reactions, and few-layer reduced graphene oxide samples were structurally and chemically investigated by the X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron spectroscopy methods, i.e. X-ray photoelectron spectroscopy (XPS) and reflection electron energy loss spectroscopy (REELS).
The commercial graphene oxide (FL-GOc) shows a stacking nanostructure of about 22×6nm average diameter by height with the distance of 0.9nm between 6-7 graphene layers, whereas the respective reduced graphene oxide (FL-RGOc)—about 8×1nm average diameter by height stacking nanostructure with the distance of 0.4nm between 2-3 graphene layers (XRD). The REELS results are consistent with those by the XRD indicating 8 (FL-GOc) and 4 layers (FL-RGOc). In graphene oxide and reduced graphene oxide prepared from the graphite the REELS indicates 8–11 and 7–10 layers. All graphene oxide samples show the C/O ratio of 2.1–2.3, 26.5–32.1 at% of C sp3 bonds and high content of functional oxygen groups (hydroxyl—COH, epoxy—COC, carbonyl—CO, carboxyl—COOH, water) (XPS). Reduction increases the C/O ratio to 2.8–10.3, decreases C sp3 content to 11.4–20.3 at% and also the content of COC and CO groups, accompanied by increasing content of COH and COOH groups. Formation of additional amount of water due to functional oxygen group reduction leads to layer delamination. Removing of functional oxygen groups and water molecules results in decreasing the distance between the graphene layers.
A ternary visible-light driven photocatalyst, Ag/BiVO
/reduced graphene oxide (rGO) composite was manufactured by hydrothermal strategy. The optimized products were characterized by XRD, SEM, HRTEM, ...EDS, XPS, DRS, Raman spectra, PL, BET, photocurrent density and EIS analysis. Compared to pure BiVO
, the fabricated ternary composite showed enhanced photocatalytic ability to decompose pollutant under visible light. Triclosan was completely removed after 100 min in solution with 1 mg/mL photocatalyst under visible light irradiation. Repeated cycle tests demonstrated the photo-stability and reusability of composite to decompose triclosan, indicating that this material could be utilized repeatedly. The upgraded photocatalytic ability was attributed to the addition of Ag and rGO, which enhanced the charge separation and inhibited the recombination of photogenerated electrons and holes. The EPR spin-trap technique (with DMPO) was performed to identify the radicals produced in Ag/BiVO
/rGO under the visible light, and trapping experiments were conducted to determine the main active species in the photocatalytic process of decomposing triclosan. Finally, seven reaction intermediates of triclosan were detected by LC-MS/MS and possible degradation routes were proposed.
•Characteristics and characterization of graphene are discussed.•Graphene synthesis methods are evaluated via cost, environment and social impacts.•Oxidative exfoliation-reduction, LPE and CVD ...potentially can be commercialized.•More work is needed to overcome environmental concerns and the high graphene cost.
Graphene and its derivatives have gained significant attention of late due to their remarkable physicochemical properties. This review focuses firstly on the synthesis methods of graphene and its derivatives along with their attributes and characterization techniques. This is followed by a discussion of the potential industrial implementation of the synthesis routes. The potential industrial implementation of the graphene synthesis methods are reviewed using the key criteria of cost, process condition, yield, scalability, product quality and environmental impact. The literature data supported that synthesis routes such as oxidative exfoliation-reduction, liquid-phase exfoliation and chemical vapor deposition have the potential to be commercialized due to their ability to produce large amount of high quality graphene. Further development is necessary to overcome barriers such as environmental concerns and the high graphene cost.
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Magnetic Fe
O
-encapsulated C
N
S
polymer/reduced graphene oxide composite (rGO-poly(C
N
S
)/Fe
O
) was synthesized to remove Pb(II) and Hg(II) from aqueous solutions. This material was characterized ...by X-ray Photoelectron Spectroscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray powder diffraction, N
adsorption, etc. The results suggest that final composite exhibits two-dimensional (2D) nanosheet structure, in which Fe
O
nanoparticles or clusters are encapsulated between the layers of rGO-poly(C
N
S
) matrix, preventing composite aggregation and nanoparticle detachment. The results of adsorption tests suggested high metal removal and short residence time to reach equilibrium. The adsorption kinetics data were well fitted by pseudo-second-order equation. The effect of metal concentration on adsorption was illustrated by Langmuir isotherm equation. Maximum metal-uptake capacities for Pb(II) and Hg(II) ions were 270.3 and 400.0 mg/g, respectively. High-resolution XPS spectra clearly illustrate the adsorption mechanism, in that Hg(II) preferentially binds to sulphur functional groups and Pb(II) tends to be adsorbed by nitrogen groups in poly(C
N
S
) matrix. Recycling performance of this composite was investigated in 15 consecutive adsorption-desorption cycles, after which the adsorption capacities for Pb(II), and Hg(II) ions remain stable thanks to Fe
O
encapsulation into the rGO-poly(C
N
S
) matrix.
An electrochemical nitrite sensor based on perovskite oxides La0·8Sr0·2MnO3 (LSM) microspheres-decorated reduced graphene oxide (rGO) composite was presented to take the merit of the excellent ...electrocatalytic activity of the LSM and the large surface area of rGO. The content of rGO has been finely adjusted and the electrochemical sensor employing 15 wt% rGO has shown an ultralow nitrite detection limit of 0.016 μM and a high sensitivity of 0.041 μA μM−1 cm−2 and 0.039 μA μM−1 cm−2 in the range of 2–100 and 100–5000 μM, respectively. In addition, the proposed electrode shows good selectivity, reproducibility and stability, suitable for detection of nitrite at various pH values. The sensor was used to determine the nitrite level in environmental water samples with acceptable relative error, demonstrating its feasibility for practical environmental monitoring.
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•A nitrite sensor combining La0·8Sr0·2MnO3 and reduced graphene oxide is developed and with an ultralow limit of detection.•The sensor maintains high sensitivity, selectivity and long-term stability, with an acceptable relative error .•The multiple oxidization states of manganese ions are responsible for the sensitivity and selectivity.
Although current energy storage devices are limited by their own shortcomings, their merits such as superior power density and cycling stability for supercapacitors (SCs), and high energy density for ...batteries cannot be ignored either. Constructing hybrid SCs (HSCs) with capacitor‐type electrodes and battery‐type electrodes can combine the advantages of SCs and batteries. Herein, a zinc‐ion HSC (ZHSC) is fabricated with a porous 3D MXene (Ti3C2Tx
)‐reduced graphene oxide aerogel cathode and zinc foil anode for the first time. As a result, the ZHSC exhibits excellent electrochemical performance with a high specific capacitance of 128.6 F g−1 at a current density of 0.4 A g−1 and a high energy density of 34.9 Wh kg−1 at a power density of 279.9 W kg−1. More importantly, after 75 000 charge and discharge cycles at a current density of 5 A g−1, the capacitance retention is still above 95% of the initial capacitance. This work provides a new way of thinking for developing high‐performance energy storage devices with superior energy, power density, and ultralong cycle life.
The MXene‐based zinc‐ion hybrid supercapacitor (ZHSC) exhibits a high energy density of 34.9 Wh kg−1 (279.9 W kg−1) and an ultralong cycle life (after 75 000 charge and discharge cycles, the capacitance retention is still above 95% of its initial capacitance), by utilizing both the battery and the capacitor‐type energy storage mechanism.
